Séminaires : Phd Seminar - Séminaire des doctorant.e.s

Equipe(s) : doctorants,
Responsables :Salim Alloun, Pedro Alves, Baptiste Dugué, Brian Flanagan, Ivory Fronteau, Kostyantyn Krutoy
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Description

Le séminaire des doctorant.e.s est l'occasion pour les doctorant.e.s de présenter des résultats et des problématiques dignes d'intérêt devant un public de non-spécialistes. L'ambiance y est informelle ; poser des questions naïves est encouragé, et les questions moins naïves sont bienvenues dans la mesure où elles n'entravent pas le bon déroulement de l'exposé.

Chaque jeudi à 18h, en alternance entre Jussieu et Sophie Germain.

The PhD seminar is an opportnuity for PhD students to present results and topics worthy of interest in front of a non-specialist audience. The mood is informal ; asking naive questions is highly encouraged and less naive questions are also welcomed, as long as they don't intefere with the smoothness of the talk.

Every Thursday at 6pm, alternating between Jussieu and Sophie Germain.

Orateur(s) Juan Pablo Vigneaux - ,
Titre Bethe entropy from a topological viewpoint
Date14/12/2017
Horaire18:00 à 19:00
Diffusion
Résume A graphical model is a graph that encodes interactions between random variables as a preferred factorisation of their joint probability distribution (the "global state"). They generalise several other models previously introduced in physics and machine learning, such as the Ising model and Bayesian networks. Several notions from statistical mechanics can be defined for these graphical models, most notably the entropy and the Gibbs free energy. These functions are difficult to compute, and Bethe introduced an approximation of the entropy that just depends on a "localised" version of the global state (its marginalisation over prescribed subsets of variables). This new function is easier to compute and gives in practice good results, even if people do not understand completely why. After introducing the concepts just described, we shall point to some topological developments (and open problems) around the Bethe approximation; for example, its interpretation in terms of graph coverings.
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